The effect of defoliation on the 3-isobutyl-2-methoxypyrazine biosynthesis in wine grapes

Field studies were conducted on Vitis vinifera cv. 'Cabernet Sauvignon' to evaluate the effects of the defoliation time (pre- and post-flowering and veraison) and severity on the 3-isobutyl-2-methoxypyrazine (IBMP) concentration and expression levels of the key related genes in grape berries. The IBMP concentration in the grapes decreased significantly at harvest after all the defoliation treatments. The earlier and heavier the defoliation treatment, the lower the IBMP concentration. The relative expression level of VvOMT3 in the berry skin was closely positively correlated with the IBMP accumulation in all the treatments. Early defoliation coupled with a 1-week delay in the harvest time may be an effective management strategy to control the IBMP concentration in grapes.